138 



ST. F^: 



specimen found here : he lias named tliis American horse Equus 

 cur\idens. Certainly it is a marvellous fact in the history of 

 the ^lammalia, that in South America a native horse should 

 ha\c lived and disappeared, to be succeeded in after ages b}- 

 the countless herds descended from the few introduced with the 

 Spanish colonists ! 



The existence in South America of a fossil horse, of the 

 mastodon, possibly of an elephant,^ and of a hollow-horned 

 ruminant, discovered by MM. Lund and Clausen in the caves of 

 Brazil, are highly interesting facts with respect to the geo- 

 graphical distribution of animals. At the present time, if we 



FOSSIL TOOTH OF HORSE, FROM BAH1.\ BLANCA. 



divide America, not by the Isthmus of Panama, but by the 

 southern part of Mexico" in lat. 20", where the great table-land 

 presents an obstacle to the migration of species, b}' affecting 

 the climate, and by forming, with the exception of some valleys 

 and of a fringe of low land on the coast, a broad barrier ; we 

 shall then have the two zoological provinces of North and South 



^ Cuvier, Ossc'niais Fossih. 



iss. 



' This IS the geographical division follo^^ed by Lichtenstein, Swainson, Erichson, 

 and Richardson. The section from Vera Cruz to Acapulco, given by Humboldt in 

 the Polit. Essay 07i Kijigdom of X. Spain will show how immense a barrier the 

 Mexican table-land forms. Dr. Richardson, in his admirable Report on the Zoology 

 of N'. America read before the Brit. Assoc. 1S36 (p. 157), talking of the identifica- 

 tion of a Mexican animal with the Syiietlieres preheiisilis, says, "We do not know 

 with what propriety, but if cori-ect, it i.s, if not a solitary instance, at least very 

 nearl)- so, of a rodent animal being common to North and South America." 



